Trait ErrorAttachment 

pub trait ErrorAttachment:
    Any
    + Debug
    + Send
    + Sync {
    // Provided method
    fn fmt_context(&self, f: &mut Formatter<'_>) -> Result { ... }
}

Additional information attached to an Error.

Besides the location in the input, which is built into errors, layers and other code can attach typed values to errors with Error::set_attachment and retrieve them with Error::attachment. An error holds at most one attachment per type. For instance the deser-path crate attaches the path of the value an error refers to.

Attachments can contribute to the Display output of the error with fmt_context.

use std::fmt;
use deser::{Error, ErrorAttachment, ErrorKind};

#[derive(Debug)]
struct FileName(String);

impl ErrorAttachment for FileName {
    fn fmt_context(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, " in {}", self.0)
    }
}

let mut err = Error::with_position(ErrorKind::InvalidType, "unexpected string", 12, 2, 5);
err.set_attachment(FileName("config.json".into()));
assert_eq!(err.attachment::<FileName>().unwrap().0, "config.json");
assert_eq!(
    err.to_string(),
    "InvalidType: unexpected string at line 2 column 5 in config.json"
);

Provided Methods

fn fmt_context(&self, f: &mut Formatter<'_>) -> Result

Writes the attachment as part of the error message.

The output is appended to the message and the location of the error, so it typically starts with a space. By default attachments are not shown.

Dyn Compatibility

This trait is dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety".

Implementors